frd Posted August 11, 2020 Share Posted August 11, 2020 26 minutes ago, southmdwatcher said: GFS 12Z----How about plentiful rains for the next two weeks. We do not need that to verify Exactly, Winds either from the South, SE or the East for days on end. Like to see the EPS later. Link to comment Share on other sites More sharing options...
yoda Posted August 11, 2020 Share Posted August 11, 2020 Flash Flood Watch posted for tomorrow for most in the region except NW VA/E WV and W MD from Hagerstown westward... 1-2 inches with potential for 4 inches in isolated areas... Flood Watch National Weather Service Baltimore MD/Washington DC 319 PM EDT Tue Aug 11 2020 DCZ001-MDZ004>006-011-013-014-016>018-503>508-VAZ025-026-029- 036>040-050>057-501-502-505>508-120400- /O.NEW.KLWX.FF.A.0020.200812T1600Z-200813T0300Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ District of Columbia-Frederick MD-Carroll-Northern Baltimore- Southern Baltimore-Prince Georges-Anne Arundel-Charles-St. Marys- Calvert-Northwest Montgomery-Central and Southeast Montgomery- Northwest Howard-Central and Southeast Howard-Northwest Harford- Southeast Harford-Augusta-Rockingham-Page-Nelson-Albemarle-Greene- Madison-Rappahannock-Orange-Culpeper- Prince William/Manassas/Manassas Park-Fairfax- Arlington/Falls Church/Alexandria-Stafford-Spotsylvania- King George-Northern Fauquier-Southern Fauquier-Western Loudoun- Eastern Loudoun-Northern Virginia Blue Ridge- Central Virginia Blue Ridge- Including the cities of Washington, Frederick, Ballenger Creek, Eldersburg, Westminster, Reisterstown, Cockeysville, Baltimore, Bowie, Suitland-Silver Hill, Clinton, College Park, Greenbelt, Laurel, Camp Springs, Glen Burnie, Annapolis, Severn, South Gate, Severna Park, Arnold, Odenton, St. Charles, Waldorf, Lexington Park, California, Chesapeake Beach, Huntingtown, Dunkirk, North Beach, Lusby, Prince Frederick, Germantown, Damascus, Bethesda, Rockville, Gaithersburg, Silver Spring, Lisbon, Columbia, Ellicott City, Jarrettsville, Aberdeen, Staunton, Waynesboro, Stuarts Draft, Harrisonburg, Luray, Shenandoah, Stanley, Lovingston, Charlottesville, Stanardsville, Madison, Orange, Gordonsville, Culpeper, Dale City, Manassas, Woodbridge, Lake Ridge, Montclair, Reston, Herndon, Annandale, Centreville, Chantilly, McLean, Franconia, Arlington, Alexandria, Falls Church, Falmouth, Fredericksburg, Dahlgren, Warrenton, Turnbull, Purcellville, Leesburg, Ashburn, Sterling, Big Meadows, and Wintergreen 319 PM EDT Tue Aug 11 2020 ...FLASH FLOOD WATCH IN EFFECT FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY EVENING... The National Weather Service in Sterling Virginia has issued a * Flash Flood Watch for portions of Maryland, The District of Columbia, and Virginia, including the following areas, in Maryland, Anne Arundel, Calvert, Carroll, Central and Southeast Howard, Central and Southeast Montgomery, Charles, Frederick, Northern Baltimore, Northwest Harford, Northwest Howard, Northwest Montgomery, Prince Georges, Southeast Harford, Southern Baltimore, and St. Marys. The District of Columbia. In Virginia, Albemarle, Arlington/Falls Church/Alexandria, Augusta, Central Virginia Blue Ridge, Culpeper, Eastern Loudoun, Fairfax, Greene, King George, Madison, Nelson, Northern Fauquier, Northern Virginia Blue Ridge, Orange, Page, Prince William, Rappahannock, Rockingham, Southern Fauquier, Spotsylvania, Stafford, and Western Loudoun. * From Wednesday afternoon through Wednesday evening * A cold front will move into the area Wednesday and then stall out. Numerous slow moving showers and thunderstorms will pose a risk of flash flooding. Thunderstorms could produce one to two inches of rain with isolated amounts up to four inches possible. PRECAUTIONARY/PREPAREDNESS ACTIONS... A Flash Flood Watch means that conditions may develop that lead to flash flooding. Flash flooding is a very dangerous situation. You should monitor later forecasts and be prepared to take action should Flash Flood Warnings be issued. Link to comment Share on other sites More sharing options...
Stormfly Posted August 11, 2020 Share Posted August 11, 2020 Nice cell over Whitemarsh Middle River area. Been tracking it on private cameras near Route 40 and Allender Rd. It just keeps training. If this picks up there's gonna be some swimming tonight. Link to comment Share on other sites More sharing options...
BlizzardNole Posted August 11, 2020 Share Posted August 11, 2020 If we are driving to Ocean City on Saturday, do we need a fanboat? Cutting the grass right now. It is HOT! Link to comment Share on other sites More sharing options...
JakkelWx Posted August 12, 2020 Share Posted August 12, 2020 Going to ocmd Saturday for the airshow. It does look much drier than the wed thru fri period so it should be mostly dry. Looking for some weenie training cells tomorrow Link to comment Share on other sites More sharing options...
DanTheMan Posted August 12, 2020 Share Posted August 12, 2020 Some storms popping up, getting a good late night soak Link to comment Share on other sites More sharing options...
George BM Posted August 12, 2020 Author Share Posted August 12, 2020 9 minutes ago, DanTheMan said: Some storms popping up, getting a good late night soak Thunder woke me up in Herndon. Link to comment Share on other sites More sharing options...
yoda Posted August 12, 2020 Share Posted August 12, 2020 2 minutes ago, George BM said: Thunder woke me up in Herndon. Woke me up here in West Springfield as I was falling asleep Link to comment Share on other sites More sharing options...
DanTheMan Posted August 12, 2020 Share Posted August 12, 2020 Several car alarms in my complex just went off with a close strike and BOOMING thunder 1 Link to comment Share on other sites More sharing options...
yoda Posted August 12, 2020 Share Posted August 12, 2020 4 minutes ago, DanTheMan said: Several car alarms in my complex just went off with a close strike and BOOMING thunder Looks like the line is slowly forming and moving slowly east too... could be one of those long term storms that last a while 1 Link to comment Share on other sites More sharing options...
yoda Posted August 12, 2020 Share Posted August 12, 2020 Yup already BULLETIN - IMMEDIATE BROADCAST REQUESTED Flood Warning National Weather Service Baltimore MD/Washington DC 355 AM EDT Wed Aug 12 2020 VAC059-153-683-685-121400- /O.NEW.KLWX.FA.W.0110.200812T0755Z-200812T1400Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ Fairfax VA-City of Manassas Park VA-Prince William VA- City of Manassas VA- 355 AM EDT Wed Aug 12 2020 The National Weather Service in Sterling Virginia has issued a * Flood Warning for... West central Fairfax County in northern Virginia... The City of Manassas Park in northern Virginia... Central Prince William County in northern Virginia... The City of Manassas in northern Virginia... * Until 1000 AM EDT Wednesday. * At 354 AM EDT, Doppler radar indicated thunderstorms producing heavy rain which will cause flooding. Up to two inches of rain have already fallen. Additional rainfall amounts of up to an inch are possible. * Some locations that will experience flooding include... Bull Run, Manassas, Sudley and Manassas Park. PRECAUTIONARY/PREPAREDNESS ACTIONS... Turn around, don`t drown when encountering flooded roads. Most flood deaths occur in vehicles. Be especially cautious at night when it is harder to recognize the dangers of flooding. Excessive runoff from heavy rainfall will cause flooding of small creeks and streams, urban areas, highways, streets and underpasses as well as other drainage areas and low lying spots. Link to comment Share on other sites More sharing options...
yoda Posted August 12, 2020 Share Posted August 12, 2020 BULLETIN - EAS ACTIVATION REQUESTED Flash Flood Warning National Weather Service Baltimore MD/Washington DC 407 AM EDT Wed Aug 12 2020 The National Weather Service in Sterling Virginia has issued a * Flash Flood Warning for... West central Fairfax County in northern Virginia... The City of Manassas Park in northern Virginia... Central Prince William County in northern Virginia... The City of Manassas in northern Virginia... * Until 800 AM EDT. * At 406 AM EDT, Doppler radar indicated thunderstorms producing heavy rain across the area. Up to three inches of rain have already fallen. Rain of one to two inches is expected in the next hour. Flash flooding is ongoing or expected to begin shortly. HAZARD...Life threatening flash flooding. Heavy rain producing flash flooding. SOURCE...Radar indicated. IMPACT...Life threatening flash flooding of creeks and streams, urban areas, highways, streets and underpasses. * Some locations that may experience flooding include... Centreville... Linton Hall... Bull Run... Manassas... Sudley... Manassas Park... 1 Link to comment Share on other sites More sharing options...
DanTheMan Posted August 12, 2020 Share Posted August 12, 2020 Manassas is getting clobbered, radar estimated 3 inches just south of me, .3ish so far in Centreville with plenty to come. Very tropical morning. Link to comment Share on other sites More sharing options...
CAPE Posted August 12, 2020 Share Posted August 12, 2020 Good read on the setup for today from Mount Holly. There will probably be plenty of areas that don't see heavy rain, or much of anything. Locations that get under a storm will get dumped on. Quote The front is expected to stall over our region today. As mentioned by the previous shift, we will have precipitable water values well above normal along and southeast of the front. As we have seen the last few days, we will likely have CAPE values getting near or above 1000 J/kg ahead of the front with little (if any) CIN. Synoptic scale lift is still quite limited (though we will be on the fringe of the right entrance region of the upper level jet by late today into this evening). However, weak mesoscale lift both along the front and along any sea and bay breezes should be more than enough for convective initiation. What is most unusual about today is the wind profiles over the region. Model soundings show wind speeds 6 kt or less through a deep layer (from the surface through approximately 450 mb). Consequently storm motions are going to be very slow (likely 5 mph or less!). Additionally, this means that bulk shear values in some areas are near zero. Bottom line is that with the weak lift and almost negligible shear, I`m not sure how widespread the coverage of showers and storms will be. However, for anything that does develop, heavy rain leading to flash flooding will be a concern. Link to comment Share on other sites More sharing options...
yoda Posted August 12, 2020 Share Posted August 12, 2020 9 minutes ago, CAPE said: Good read on the setup for today from Mount Holly. There will probably be plenty of areas that don't see heavy rain, or much of anything. Locations that get under a storm will get dumped on. LWX seems the total opposite in their morning AFD if I am reading what you posted right Quote NEAR TERM /UNTIL 6 PM THIS EVENING/... Weak upper level disturbance moving over the region presently has caused a late-night outbreak of thunderstorms. Heavy rain is common given the high PW`s and slow motion. Think flash flooding with this initial burst of storms today will be isolated, but have considered extending watch to start presently. Will monitor radar trends. Should see a lull with some sun later this morning as the upper disturbance moves away. Then another, more potent disturbance will move in along with the surface front, spelling a more significant round of heavy thunderstorms. Certainly will have some isolated severe risk, but with slow motions, high PW`s and wet antecedent conditions in many areas, a significant flash flood threat exists. Highs will reach the low 90s before the storms re-erupt, possibly for the last time for several days. && Link to comment Share on other sites More sharing options...
H2O Posted August 12, 2020 Share Posted August 12, 2020 Early morning storms Link to comment Share on other sites More sharing options...
CAPE Posted August 12, 2020 Share Posted August 12, 2020 1 minute ago, yoda said: LWX seems the total opposite in their morning AFD if I am reading what you posted right Not really. LWX doesn't mention how widespread the coverage will, or wont be, while Mount Holly went into more detail on the mechanisms that will be in place for storm initiation, as well as uncertainty on the coverage due to weak lift/ shear. Bottom line is there will be some slow moving cells that will drop a lot of rain in a short amount of time, thus the FFW. Link to comment Share on other sites More sharing options...
CAPE Posted August 12, 2020 Share Posted August 12, 2020 WPC has the region in a moderate risk for excessive rainfall. Quote .THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER THE HEART OF THE MID ATLANTIC URBAN CORRIDOR... ...Eastern U.S... There is a marked potential for scattered intense rainfall today, which first appears as a local maximum in the hi-res model consensus, but when one zooms in it comes more fully into focus. It is difficult to outline a Moderate Risk area for flash flooding associated with loosely organized summertime convection within weak low level inflow winds. Today, however, we have the heaviest model signal located across an area that is both urban and already saturated, and the environmental signal for heavy local rainfall rates is pretty exceptional. The 00Z KIAD sounding at Dulles Airport was particularly telling, with steep lapse rates and little inhibition, coupled with nearly a 2.00 inch precipitable water value. An upper trough is merely brushing across the top of this region, and into northern New England, and while this will provide only minimal lift, it will drop a cold front into position across southern Pennsylvania to near NYC by midday, helping to focus the pool of moisture and instability over the Mid-Atlantic states. Models forecast a swath of MUCAPE 2000 J/kg or more in the Moderate Risk area. Consumption of this instability pool may be chaotic, owing to storm initiation along sea breezes, mountain ridges, and outflows. But the net effect is usually for fairly broad scale overturning, resulting in scattered very heavy rain. In recent events the HREF has been good at placing the general axis of heaviest rainfall, and today that axis is essentially right along I-95 from Philadelphia to Washington D.C., and also cutting across the wet soil footprint left behind by a soggy 2-week period. We expect to see 2.0 inch PW in the pre convective environment, and note that the NAM Nest produces spotty 3-inch per hour rain rates today. That model frequently produces 2.0 to 2.50 inch rain rates, but rates of 3 are fairly rare in the model. This seems entirely plausible given the moisture, instability, and mean 0-6 km winds of only zero to five knots. Although there is not enough shear for well organized storms or training, the individual cells should be very robust and efficient, as well as nearly stationary. Link to comment Share on other sites More sharing options...
yoda Posted August 12, 2020 Share Posted August 12, 2020 Yikes PRELIMINARY LOCAL STORM REPORT NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 556 AM EDT WED AUG 12 2020 ..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON... ..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE.... ..REMARKS.. 0554 AM FLASH FLOOD 1 WNW MANASSAS PARK 38.78N 77.47W 08/12/2020 CITY OF MANASSAS VA 911 CALL CENTER ROAD CLOSED DUE TO A SINKHOLE AT THE INTERSECTION OF MOSEBY CT. AND MOSEBY DR. Link to comment Share on other sites More sharing options...
yoda Posted August 12, 2020 Share Posted August 12, 2020 6 minutes ago, CAPE said: WPC has the region in a moderate risk for excessive rainfall. Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 429 AM EDT Wed Aug 12 2020 Day 1 Valid 01Z Wed Aug 12 2020 - 12Z Wed Aug 12 2020 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER THE HEART OF THE MID ATLANTIC URBAN CORRIDOR... ...Eastern U.S... There is a marked potential for scattered intense rainfall today, which first appears as a local maximum in the hi-res model consensus, but when one zooms in it comes more fully into focus. It is difficult to outline a Moderate Risk area for flash flooding associated with loosely organized summertime convection within weak low level inflow winds. Today, however, we have the heaviest model signal located across an area that is both urban and already saturated, and the environmental signal for heavy local rainfall rates is pretty exceptional. The 00Z KIAD sounding at Dulles Airport was particularly telling, with steep lapse rates and little inhibition, coupled with nearly a 2.00 inch precipitable water value. An upper trough is merely brushing across the top of this region, and into northern New England, and while this will provide only minimal lift, it will drop a cold front into position across southern Pennsylvania to near NYC by midday, helping to focus the pool of moisture and instability over the Mid-Atlantic states. Models forecast a swath of MUCAPE 2000 J/kg or more in the Moderate Risk area. Consumption of this instability pool may be chaotic, owing to storm initiation along sea breezes, mountain ridges, and outflows. But the net effect is usually for fairly broad scale overturning, resulting in scattered very heavy rain. In recent events the HREF has been good at placing the general axis of heaviest rainfall, and today that axis is essentially right along I-95 from Philadelphia to Washington D.C., and also cutting across the wet soil footprint left behind by a soggy 2-week period. We expect to see 2.0 inch PW in the pre convective environment, and note that the NAM Nest produces spotty 3-inch per hour rain rates today. That model frequently produces 2.0 to 2.50 inch rain rates, but rates of 3 are fairly rare in the model. This seems entirely plausible given the moisture, instability, and mean 0-6 km winds of only zero to five knots. Although there is not enough shear for well organized storms or training, the individual cells should be very robust and efficient, as well as nearly stationary. The flash flood threat may only last for about 4 hours, give or take, along the urban corridor, beginning around 17Z, but within that short period there may be some significant flash flooding. Link to comment Share on other sites More sharing options...
yoda Posted August 12, 2020 Share Posted August 12, 2020 Map version Link to comment Share on other sites More sharing options...
BlizzardNole Posted August 12, 2020 Share Posted August 12, 2020 There will be some places that get very heavy rain, but I fully expect to be out watering my hardpan, parched gardens tonight. I am looking forward to lower temps starting tomorrow. Link to comment Share on other sites More sharing options...
mappy Posted August 12, 2020 Share Posted August 12, 2020 i guess i haven't been following closely enough to understand all the flood watches and excessive rainfall forecast. haven't seen shit for rain up here Link to comment Share on other sites More sharing options...
CAPE Posted August 12, 2020 Share Posted August 12, 2020 10 minutes ago, mappy said: i guess i haven't been following closely enough to understand all the flood watches and excessive rainfall forecast. haven't seen shit for rain up here It's because the set up is favorable for isolated to scattered convection, with high pwats and little in the way of steering flow. Hard to pinpoint exactly where this will occur, thus the broad brush flood watch. So yeah not everyone will see the heavy rain, but for places that do, it may be excessive, and given the recent bouts of heavy rain it wont take too much to cause flash flooding in the more saturated areas. 1 Link to comment Share on other sites More sharing options...
CAPE Posted August 12, 2020 Share Posted August 12, 2020 Looks like the trend on the latest guidance is for the High over SE Canada to nudge far enough south to give us a mostly dry weekend. It wont be "perfect", but more comfortable with temps in the low to mid 80s and somewhat lower dew points Link to comment Share on other sites More sharing options...
mappy Posted August 12, 2020 Share Posted August 12, 2020 15 minutes ago, CAPE said: It's because the set up is favorable for isolated to scattered convection, with high pwats and little in the way of steering flow. Hard to pinpoint exactly where this will occur, thus the broad brush flood watch. So yeah not everyone will see the heavy rain, but for places that do, it may be excessive, and given the recent bouts of heavy rain it wont take too much to cause flash flooding in the more saturated areas. thanks! i should probably pay attention more 1 Link to comment Share on other sites More sharing options...
Jrlg1181 Posted August 12, 2020 Share Posted August 12, 2020 54 minutes ago, mappy said: i guess i haven't been following closely enough to understand all the flood watches and excessive rainfall forecast. haven't seen shit for rain up here Same here....probably the only place in Va that can say that... massive rain totals just minutes away in all directions ...1.72 inches Link to comment Share on other sites More sharing options...
MN Transplant Posted August 12, 2020 Share Posted August 12, 2020 3 hours ago, CAPE said: Good read on the setup for today from Mount Holly. There will probably be plenty of areas that don't see heavy rain, or much of anything. Locations that get under a storm will get dumped on. I'm going to call this a no-dograph. 1 Link to comment Share on other sites More sharing options...
adelphi_sky Posted August 12, 2020 Share Posted August 12, 2020 I got a spit from that storm. 0.14" Heard a few good LONG rumbles of thunder. That's about it. Link to comment Share on other sites More sharing options...
Eskimo Joe Posted August 12, 2020 Share Posted August 12, 2020 NAM-Nest and HRRR like northern MD. Everyone else loses. 1 Link to comment Share on other sites More sharing options...
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