Eskimo Joe Posted January 30, 2021 Share Posted January 30, 2021 Updated LWX AFD: Quote AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 900 PM EST FRI JAN 29 2021 .SYNOPSIS... HIGH PRESSURE WILL BUILD OVERHEAD TODAY THROUGH SATURDAY. LOW PRESSURE WILL APPROACH FROM THE WEST SUNDAY AND TRANSFER OFF THE COAST ON MONDAY. HIGH PRESSURE WILL BUILD BACK IN BY THE MIDDLE OF THE WEEK. && .NEAR TERM /THROUGH SATURDAY/... 9:00 PM UPDATE: NO SIGNIFICANT CHANGES TO THE FORECAST AT THIS TIME ACROSS THE AREA. MAIN CHANGE FOR TONIGHT WAS TO DECREASE WIND SPEEDS ACROSS THE AREA A LITTLE QUICKER, AND TAKE WIND CHILL VALUES UP A FEW DEGREES OVERALL. OTHER THAN THAT, STILL EXPECTING A DRY NIGTH UNDER MOSTLY CLEAR SKIES FOR MUCH OF THE AREA. CLOUDS WILL LINGER ACROSS NORTHEAST MD AND FAR NORTHERN VA FOR A WHILE LONGER THOUGH, BEFORE EVENTUALLY CLEARING OUT BY DAYBREAK. SEE PREVIOUS NEAR TERM FOR MORE DETAILS ON THE FORECAST THROUGH SATURDAY. PREVIOUS DISCUSSION: WINDS SHOULD GRADUALLY DECREASE IN MAGNITUDE OVERNIGHT AS HIGH PRESSURE STARTS TO APPROACH FROM THE WEST, BUT THE COLD AIR WILL REMAIN IN PLACE. LOWS TONIGHT WILL BOTTOM OUT IN THE TEENS FOR MOST, WITH LOWER 20S POSSIBLE IN DOWNTOWN DC. HIGH PRESSURE WILL BUILD OVERHEAD DURING THE DAY TOMORROW, BRINGING QUIET WEATHER CONDITIONS TO THE AREA. SKIES WILL START OUT SUNNY, BUT HIGH CLOUDS WILL BEGIN TO STREAM IN ALOFT IN ADVANCE OF THE NEXT SYSTEM APPROACHING FROM THE WEST BY DAY'S END. HIGHS TOMORROW WILL TOP OUT IN THE 30S TO NEAR 40. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... 9:00 PM UPDATE: NO CHANGE TO THE PREVIOUS FORECAST AT THIS TIME, BUT SOME INCREASE IN EXPECTED SNOW TOTALS MAY BE NECESSARY IN THE NEXT SHIFT. MODEL GUIDANCE CONTINUE TO INCREASE IN CONFIDENCE OF 4-7" FOR MOST AREAS ALONG AND WEST OF I-95, WITH THE HIGHER END OF THAT STARTING TO LOOK A LITTLE MORE LIKELY. WOULD LIKE TO SEE ANOTHER ROUND OF GUIDANCE BEFORE BUMPING THINGS UP JUST YET. FOR NOW, SEE THE PREVIOUS UPDATE AND DISCUSISON FOR MORE DETAILED THOUGHTS. 7:30 PM UPDATE: ONLY CHANGE TO THE SHORT TERM FORECAST WAS A SLIGHT UPTICK ACROSS WESTERN PORTIONS OF THE FORECAST AREA IN TERMS OF SNOW TOTALS. THINK A STEADIER BAND OF SNOW MAY SLIDE IN RATHER EARLY ON SUNDAY MORNING ACROSS THE EATERN WV AND WESTERN MD. HAVE ADDED ALL REMAINING AREAS (WESTERN AND NORTHERN MD, AS WELL AS THE REST OF EASTERN WV) TO THE WINTER STORM WATCH. SEE THE LATES SNOWFALL FORECAST AT WEATHER.GOV/WASHINGTON/WINTER. PREVIOUS DISCUSSION: ATTENTION WILL TURN TO A SYSTEM TRACKING INTO THE OHIO VALLEY SATURDAY NIGHT. A SURGE OF WARM ADVECTION ALOFT IN ADVANCE OF THE SURFACE LOW/CLOSED UPPER LOW TRACKING INTO THE OHIO VALLEY WILL START TO OVERSPREAD THE AREA FROM SOUTHWEST TO NORTHEAST OVER THE COURSE OF THE NIGHTTIME HOURS. SNOW MAY BE POSSIBLE ACROSS CENTRAL VIRGINIA AND THE CENTRAL SHENANDOAH VALLEY AS EARLY AS MIDNIGHT, AND SHOULD REACH THE DC METRO BY AROUND OR SHORTLY BEFORE DAYBREAK. THE ONSET OF SNOW MAY HOLD OFF A COUPLE OF HOURS LATER IN THE BALTIMORE METRO AREA. A STEADY PERIOD OF SNOW IS EXPECTED ACROSS THE ENTIRE AREA ON SUNDAY IN ASSOCIATION WITH THIS PUSH OF WARM ADVECTION. A GENERAL 4-6 INCHES OF SNOW IS EXPECTED ACROSS THE AREA WITH THIS ROUND OF SNOW. AS A RESULT, A WINTER STORM WATCH HAS BEEN ISSUED FOR MOST OF THE FORECAST AREA. MODEL GUIDANCE SHOWS A DRY SLOT MOVING IN ALOFT SUNDAY EVENING. THIS DRY SLOT APPEARS AS THOUGH IT MAY SHUT OFF ICE CRYSTAL PRODUCTION FOR MUCH OF SUNDAY NIGHT, WITH SATURATION IN MODEL SOUNDINGS EVIDENT ONLY UP TO BETWEEN -5 AND -10 C. WITHOUT DEEPER SATURATION, PRECIPITATION SHOULD BE MUCH LIGHTER, AND MAY FALL LARGELY IN THE FORM OF FREEZING DRIZZLE/LIGHT FREEZING RAIN, WITH LIGHT SNOW AND SLEET ALSO POSSIBLE IF ICE CRYSTALS ARE ABLE TO FORM. AS A RESULT, NOT MUCH ADDITIONAL SNOW ACCUMULATION IS EXPECTED SUNDAY NIGHT, ALTHOUGH THERE MAY BE A LIGHT GLAZE OF ICE IN MANY AREAS. WARMER AIR MAY WORK INTO SOUTHERN MARYLAND, WHERE A CHANGEOVER TO PLAIN RAIN WILL LIKELY OCCUR. && .LONG TERM /MONDAY THROUGH FRIDAY/... BY MONDAY, THE UPPER TROUGH/LOW WILL BE MOVING OVERHEAD AND THE SURFACE LOW WILL TRANSFER TO THE COAST, LIKELY SOMEWHERE BETWEEN CAPE HATTERAS AND THE DELMARVA. AS COLDER AIR MOVES IN ALOFT ASSOCIATED WITH THE UPPER TROUGH AND MOISTURE DEEPENS ONCE AGAIN, PRECIPITATION TYPE WILL LIKELY TRANSITION TO SNOW, THOUGH SOME RAIN IS POSSIBLE DEPENDING ON HOW FAR WARM AIR WORKS INLAND. THIS PART OF THE FORECAST REMAINS TRICKY, BECAUSE ADDITIONAL SNOW ACCUMULATIONS WILL BE DEPENDENT ON THE EVOLUTION OF THE LOW AND MESOSCALE FEATURES. SO ADDITIONAL SNOW TOTALS COULD RANGE FROM BEING VERY MINIMAL TO HAVING A LOCALIZED ZONE OF ADDITIONAL MODERATE OR HEAVY SNOW. SNOW WILL LIKELY TAPER OFF MONDAY NIGHT AS THE LOW PULLS AWAY TO THE NORTHEAST. SOME PRECIPITATION MAY LINGER INTO TUESDAY ALONG I- 95 AS WELL AS UPSLOPE ZONES, BUT THE IMPACTFUL PRECIPITATION WILL BE OVER BY THEN. OTHERWISE, GUSTY NORTHWEST WINDS WILL DEVELOP AS THE LOW STRENGTHENS, AND TEMPERATURES WILL REMAIN CHILLY. Link to comment Share on other sites More sharing options...
snowfan Posted January 30, 2021 Share Posted January 30, 2021 1 minute ago, stormtracker said: what? it's only at 69 hours. Prob should wait until we get to the time period where the back end starts. It was dry for the most for us on the back end. Most of us get about .1 from hr60 to hr84. Link to comment Share on other sites More sharing options...
BristowWx Posted January 30, 2021 Share Posted January 30, 2021 1 minute ago, MN Transplant said: Our worst-case scenario seems to be the 00z NAM Nest dry front side and the 00z 12km NAM dry backside. That’s about a 3” storm for many of us along 95. I think the backside will moisten up some. At least I hope or it’s gonna be a painful process. 2 Link to comment Share on other sites More sharing options...
yoda Posted January 30, 2021 Share Posted January 30, 2021 Just now, stormtracker said: what hour on PW tho? Because at 18z the back end didn't start until like 72/78 hours? 84. See @MN Transplant post last psage about it 1 Link to comment Share on other sites More sharing options...
BTRWx's Thanks Giving Posted January 30, 2021 Share Posted January 30, 2021 LWX is now 6-8" for D.C. 1 Link to comment Share on other sites More sharing options...
MN Transplant Posted January 30, 2021 Share Posted January 30, 2021 4 minutes ago, snowfan said: It was dry for the most for us on the back end. Most of us get about .1 from hr60 to hr84. We get the 700 wind vector pointed at us, but it is not a nice moist fetch off the ocean, it is a very long route over NYC and the coming in from the north. Just not much left by the time it gets here. 06z Monday to 06z Tuesday. Not much after either. 1 2 Link to comment Share on other sites More sharing options...
SnowGolfBro Posted January 30, 2021 Share Posted January 30, 2021 1 hour ago, JakkelWx said: I drew that map for my backyard. And welcome back Bob! Good Omen Link to comment Share on other sites More sharing options...
jayyy Posted January 30, 2021 Share Posted January 30, 2021 19 minutes ago, psuhoffman said: I know it’s the SREF but it’s still better for them to look good then bad. And they look VERY good. Always good to have in your camp. Never good if it’s the only one in your camp, however Link to comment Share on other sites More sharing options...
SnowCane Posted January 30, 2021 Share Posted January 30, 2021 1 minute ago, BTRWx's Thanks Giving said: LWX is now 6-8" for D.C. Pics or it didn’t happen Link to comment Share on other sites More sharing options...
winterymix Posted January 30, 2021 Share Posted January 30, 2021 2 minutes ago, MN Transplant said: Our worst-case scenario seems to be the 00z NAM Nest dry front side and the 00z 12km NAM dry backside. That’s about a 3” storm for many of us along 95. My amateur look at this evening's NAM prompts this question to a/any meteorologist: Check out the 700 mb evolution: 700 meanders SW to NE at Ohio River valley and weakens... and then reforms in the mid-Atlantic states moving east and intensifying over eastern Delaware. It warms and dry-slots us. Are we s-------d or is NAM incorrect? Link to comment Share on other sites More sharing options...
Wonderdog Posted January 30, 2021 Share Posted January 30, 2021 5 minutes ago, BristowWx said: I think the backside will moisten up some. At least I hope or it’s gonna be a painful process. Just remember, it's a Miller B. Link to comment Share on other sites More sharing options...
hobbes9 Posted January 30, 2021 Share Posted January 30, 2021 1 minute ago, SnowCane said: Pics or it didn’t happen I found the ice interesting as well. 1 1 Link to comment Share on other sites More sharing options...
BTRWx's Thanks Giving Posted January 30, 2021 Share Posted January 30, 2021 2 minutes ago, SnowCane said: Pics or it didn’t happen 1 1 Link to comment Share on other sites More sharing options...
ers-wxman1 Posted January 30, 2021 Share Posted January 30, 2021 NAM 500 trough is swinging across positively tilted and the upper low is closed, but the best forcing is generally north of where the closed circulation crosses. Trough needs to swing across neutral or even a bit negative tilt. Coastal does not get captured or tuck where it needs to and we torch, stay out of the CCB. 2 1 Link to comment Share on other sites More sharing options...
MN Transplant Posted January 30, 2021 Share Posted January 30, 2021 4 minutes ago, winterymix said: My amateur look at this evening's NAM prompts this question to a/any meteorologist: Check out the 700 mb evolution: 700 meanders SW to NE at Ohio River valley and weakens... and then reforms in the mid-Atlantic states moving east and intensifying over eastern Delaware. It warms and dry-slots us. Are we s-------d or is NAM incorrect? Yeah, it’s a transfer. You can see the 12z Euro does the same, just with a different, more southerly orientation that helps us out some. Link to comment Share on other sites More sharing options...
Negnao Posted January 30, 2021 Share Posted January 30, 2021 1 minute ago, Wonderdog said: Just remember, it's a Miller B. That’s why I liked the euro runs with a weaker coastal that went E rather than NE up the coast from our latitude. Wasn’t a blockbuster but it was clean. Link to comment Share on other sites More sharing options...
DCAlexandria Posted January 30, 2021 Share Posted January 30, 2021 NAM 500 trough is swinging across positively tilted and the upper low is closed, but the best forcing is generally north of where the closed circulation crosses. Trough needs to swing across neutral or even a bit negative tilt. Coastal does not get captured or tuck where it needs to and we torch, stay out of the CCB. At least it’s just the nam. 1 Link to comment Share on other sites More sharing options...
Eskimo Joe Posted January 30, 2021 Share Posted January 30, 2021 LWX's new snow map is decent. Would be the biggest event for many in several years and meet or exceed January climo for IAD, DCA, and BWI. 2 Link to comment Share on other sites More sharing options...
csnavywx Posted January 30, 2021 Share Posted January 30, 2021 There will probably be some drizzle and freezing drizzle once the dry slot rolls in. Could be an extended period of it too. The reason is that cloud top temps warm above -10C as the dry slot erodes it away, leaving no very few ice crystals available for snow formation. Still plenty of moisture underneath that and some background lift though, so there will be drizzle. That's going to be an issue until/unless the coastal low can set up a reasonable def. zone and ccb to remoisten the column. 3 Link to comment Share on other sites More sharing options...
WinterWxLuvr Posted January 30, 2021 Share Posted January 30, 2021 Just now, Eskimo Joe said: IMO, LWX's new snow map is decent but given the NAMs being bad for us, I don't see it going any higher. I was just thinking that it’s interesting when the pros see things one way and weenies see it another. I can’t say for certain but I highly doubt they are hanging their forecast on the NAMfrom this range 1 Link to comment Share on other sites More sharing options...
Maestrobjwa Posted January 30, 2021 Share Posted January 30, 2021 19 minutes ago, WinterWxLuvr said: Hard to put much faith in the NAM past about 36 hours. That's what I'm saying, lol Is it really worth parsing (pr panicking over) the details of it right now? Link to comment Share on other sites More sharing options...
ers-wxman1 Posted January 30, 2021 Share Posted January 30, 2021 3 minutes ago, DCAlexandria said: At least it’s just the nam . Attention should be paid to it. The NAM even beyond 48 hours can give insight into how the smaller details may be evolving. Guidance is guidance. We shouldn’t look at it’s QPF verbatim, but more so to understand it’s evolution. 4 1 Link to comment Share on other sites More sharing options...
Chris78 Posted January 30, 2021 Share Posted January 30, 2021 Just now, WinterWxLuvr said: I was just thinking that it’s interesting when the pros see things one way and weenies see it another. I can’t say for certain but I highly doubt they are hanging their forecast on the NAMfrom this range This. I'm sure Lwx isn't second guessing there snow map because of a NAM run from 48 hours out. Lol. 1 Link to comment Share on other sites More sharing options...
high risk Posted January 30, 2021 Share Posted January 30, 2021 Just now, ers-wxman1 said: Attention should be paid to it. The NAM even beyond 48 hours can give insight into how the smaller details may be evolving. Guidance is guidance. We shouldn’t look at it’s QPF verbatim, but more so to understand it’s evolution. Correct. Everyone laughed back in December when the NAM was the first model to show that storm coming much further west and ruining chances for heavy snow along the I-95 corridor. That doesn't at all mean that it's correct now, but to completely dismiss it at this stage comes with risk. 5 1 1 Link to comment Share on other sites More sharing options...
Eskimo Joe Posted January 30, 2021 Share Posted January 30, 2021 6 minutes ago, high risk said: Correct. Everyone laughed back in December when the NAM was the first model to show that storm coming much further west and ruining chances for heavy snow along the I-95 corridor. That doesn't at all mean that it's correct now, but to completely dismiss it at this stage comes with risk. You and I are on the same page, NAM kept bumping that mix line NW and folks just laughed it off until it became clear things were going that way. Also wanted to say that somehow when I quoted this post it added a ''laugh'' reaction and I can't change it because I hit my limit for the day. Weird. 1 5 Link to comment Share on other sites More sharing options...
yoda Posted January 30, 2021 Share Posted January 30, 2021 00z RGEM keeps most of the LWX CWA in snow through 54 Link to comment Share on other sites More sharing options...
stormtracker Posted January 30, 2021 Author Share Posted January 30, 2021 RGEM is better than 18z. Back end love is real. Flip between the two 1 Link to comment Share on other sites More sharing options...
psuhoffman Posted January 30, 2021 Share Posted January 30, 2021 10 minutes ago, high risk said: Correct. Everyone laughed back in December when the NAM was the first model to show that storm coming much further west and ruining chances for heavy snow along the I-95 corridor. That doesn't at all mean that it's correct now, but to completely dismiss it at this stage comes with risk. What was odd was the mslp actually improved slightly but the storm had a “blown out” look to it and never wrapped back up. Very odd to have a captured tucked low off OC and all the precip is up in PA. ETA: ehh on second look the low gets captured further north then I thought on first glacé. 1 Link to comment Share on other sites More sharing options...
yoda Posted January 30, 2021 Share Posted January 30, 2021 1 minute ago, stormtracker said: RGEM is better than 18z. Back end love is real. Flip between the two @mappy cleans up Link to comment Share on other sites More sharing options...
BristowWx Posted January 30, 2021 Share Posted January 30, 2021 Just now, Hypothetical 240 hour snow said: RGEM out to lunch in its fantasy land unfortunately. Why? Link to comment Share on other sites More sharing options...
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