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June 16th-17th Floodmageddon


eurojosh

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THE NATIONAL WEATHER SERVICE IN STERLING VIRGINIA HAS ISSUED A

* FLASH FLOOD WATCH FOR PORTIONS OF MARYLAND...THE DISTRICT OF
COLUMBIA...VIRGINIA AND WEST VIRGINIA...INCLUDING THE
FOLLOWING AREAS...IN MARYLAND...ANNE ARUNDEL...CARROLL...
CENTRAL AND EASTERN ALLEGANY...CENTRAL AND SOUTHEAST HOWARD...
CENTRAL AND SOUTHEAST MONTGOMERY...EXTREME WESTERN ALLEGANY...
FREDERICK MD...NORTHERN BALTIMORE...NORTHWEST HOWARD...
NORTHWEST MONTGOMERY...PRINCE GEORGES...SOUTHERN BALTIMORE AND
WASHINGTON. THE DISTRICT OF COLUMBIA. IN VIRGINIA...
ARLINGTON/FALLS CHURCH/ALEXANDRIA...CLARKE...CULPEPER...
EASTERN LOUDOUN...FAIRFAX... FREDERICK VA ( :lol:)

...MADISON...NORTHERN
FAUQUIER...NORTHERN VIRGINIA BLUE RIDGE...PAGE...PRINCE
WILLIAM/MANASSAS/MANASSAS PARK...RAPPAHANNOCK...ROCKINGHAM...
SHENANDOAH...SOUTHERN FAUQUIER...WARREN AND WESTERN LOUDOUN.
IN WEST VIRGINIA...BERKELEY...EASTERN GRANT...EASTERN
MINERAL...HAMPSHIRE...HARDY...JEFFERSON...MORGAN...WESTERN
GRANT AND WESTERN MINERAL.

* FROM THIS AFTERNOON THROUGH LATE TONIGHT

* THUNDERSTORMS WITH HEAVY RAINFALL ( :lol: ) ARE EXPECTED LATE TODAY AND
TONIGHT. REPEATED THUNDERSTORMS ( :lol:  :lol:  :lol:  :lol:  :lol: ) WITH HEAVY RAINFALL OVER THE

SAME AREAS MAY RESULT IN FLASH FLOODING.

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Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
400 AM EDT THU JUN 16 2016

.NEAR TERM /THROUGH FRIDAY/...
Unusual weather situation for mid-June unfolding at present. A
closed 500 mb low with very strong dynamics is currently centered
over Lake Michigan. This system is progged to move southeastward
and cross West Virginia and Virginia late tonight into
Friday...accompanied by a surface low and cold front.
Meanwhile...a stationary front has set up shop over our region and
will not move a great deal until the surface low passes. South of
the warm front...air temperatures will likely warm quite a bit
today with low 90s expected in central Virginia...a stark contrast
to the mid 70s expected over northeastern Maryland. Between these
two areas a great deal of uncertainty exists about the actual
high...as the front is expected to shift northeast a bit more this
morning...and then shift back southwest later this afternoon and
this evening. Thus...while we are forecasting near 80 in Baltimore
and mid 80s in DC...its not impossible this forecast will bust by
several degrees either side of that.
While some scattered showers
and isolated thunder continues at this time...we expect some
clearing to occur in much of the area for a time later this
morning between the current weak shortwave passing across the area
and the main system.

Southerly flow will continue to bring very moist air north into
locations south of the front...while winds aloft will be
increasing as the low approaches...resulting in better wind threat
as well as more organizational possibilities due to better shear.
End result...we have a really good shot at some pretty strong
thunderstorms later today and this evening...mainly in areas near
and south of the warm front. The SPC has increased the threat to
enhanced risk across southwestern portions of the CWA while the
slight risk has been expanded across DC metro towards Baltimore.

That having been said...this again depends on the position the
front takes later today...with a more southwestward shift likely
to reduce the severe threat in DC and Baltimore. Main severe
threat is damaging winds given strong winds aloft and warm
atmosphere limiting hail potential...but near the stationary
front an isolated tornado couldn`t be ruled out.

Besides the severe threat...we also have potential heavy rain to
deal with. Some guidance has been hitting the heavy rain threat
hard...the NAM and ECMWF being notable among them
. PW`s being
expected to reach near 2" this afternoon...with potential for
training along the frontal boundary already in place...suggests we
will have a threat for flash flooding despite the recent dry
weather. Therefore...will raise flash flood threat shortly. Flash
flooding threat is highest this evening...but kept watch going
thru the night given expectation of continued rain as the system
pushes across the area.

The system will slide southeast of us through the day Friday with
rain diminishing and some clearing likely later on. Highs will be
notably cooler across the board with the Canadian air mass pushing
in.

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DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1254 AM CDT THU JUN 16 2016

VALID 161200Z - 171200Z

...THERE IS AN ENH RISK OF SVR TSTMS ACROSS PARTS OF ERN

OH...WV...VA...SW PA AND WRN MD...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE UPPER OH

VALLEY...SRN TO CNTRL APPALACHIANS AND MID-ATLANTIC OUTSIDE OF THE

ENHANCED RISK AREA...


...SUMMARY...

AN ENHANCED WIND DAMAGE THREAT ALONG WITH POTENTIAL FOR A COUPLE

TORNADOES IS FORECAST THIS AFTERNOON ACROSS THE UPPER OHIO VALLEY

INTO THE SOUTHERN TO CENTRAL APPALACHIAN MOUNTAINS AND EASTWARD INTO

THE MID-ATLANTIC STATES. SEVERE STORMS WITH ISOLATED LARGE HAIL AND

WIND DAMAGE WILL ALSO BE POSSIBLE THIS AFTERNOON AND EVENING ACROSS

PARTS OF THE NORTHERN PLAINS. MARGINALLY SEVERE STORMS WITH HAIL AND

STRONG WIND GUSTS MAY ALSO OCCUR ACROSS THE MID MISSOURI

VALLEY...MID MISSISSIPPI VALLEY...CENTRAL TO EASTERN GULF COAST

STATES AND CAROLINAS.

...UPPER OH VALLEY/SRN AND CNTRL APPALACHIANS/MID-ATLANTIC STATES...

AN UPPER-LEVEL TROUGH WILL MOVE SEWD FROM THE GREAT LAKES REGION

INTO THE UPPER OH VALLEY TODAY. AT THE SFC...A LOW WILL MOVE SEWD

INTO THE MID-ATLANTIC STATES AS A COLD FRONT ADVANCES SEWD INTO THE

SRN AND CNTRL APPALACHIAN MTNS. A MOIST AIRMASS WILL BE IN PLACE

AHEAD OF THE TRACK OF THE SFC LOW WITH MODERATE INSTABILITY ACROSS

MUCH OF THE MID-ATLANTIC REGION BY EARLY AFTERNOON. THUNDERSTORMS

APPEAR LIKELY TO FIRST INITIATE AROUND LAKE ERIE AROUND MIDDAY WITH

A LINEAR CONVECTIVE SYSTEM ORGANIZING AND MOVING SEWD INTO THE CNTRL

APPALACHIAN MTNS DURING THE AFTERNOON. THIS CONVECTION MAY REACH THE

MID-ATLANTIC COAST DURING THE EVENING OR OVERNIGHT PERIOD.

CONCERNING THE SEVERE THREAT...BOTH THE NAM AND GFS SOLUTIONS ARE IN

AGREEMENT WITH THE PLACEMENT OF AN AXIS OF MODERATE

INSTABILITY...EXTENDING FROM NRN VA NWWD INTO SW PA BY EARLY

AFTERNOON. LOOKING AT NAM AND RAP FORECAST SOUNDINGS ALONG THIS

CORRIDOR AT 21Z...SFC DEWPOINTS SHOULD BE IN THE MID 60S IN THE

CNTRL APPALACHIANS WITH LOWER 70S F POSSIBLE IN THE LOWER ELEVATIONS

OF THE MID-ATLANTIC. THIS WILL CONTRIBUTE TO MODERATE INSTABILITY

WITH MLCAPE VALUES REACHING 1500 TO 2000 J/KG BY MID-AFTERNOON WITH

CONSIDERABLE DCAPE. THE WIND PROFILE IS FORECAST TO BE

UNIDIRECTIONAL WITH SUBSTANTIAL SPEED SHEAR IN THE MID-LEVELS. THIS

ENVIRONMENT SHOULD BE FAVORABLE FOR DAMAGING WIND GUSTS ESPECIALLY

IF A LINEAR CONVECTIVE SYSTEM CAN ORGANIZE AS IS SUGGESTED BY THE

WRF-NSSL HIGH RESOLUTION MODEL. HAVE INTRODUCED AN ENHANCED RISK

AREA FROM ERN OH SEWD INTO CNTRL VA WHERE THE POTENTIAL FOR A

CLUSTER OF WIND DAMAGE REPORTS APPEARS TO THE GREATEST.

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Having trouble finding the line that is in OH/WPA on the models (HRRR/4kNAM)... They all had activitiy going up closer to noon in that area... Could this have any impact downstream'?

 

Yeah, the models didn't catch that well.  HRRR has some semblance of it but the real game fires up closer to Toledo later on, as you say.

 

Here's the 11z run

 

post-1746-0-33968900-1466080855_thumb.pn

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Pretty important differences in the HRRR and 4km NAM and how tonight plays out.

 

The HRRR brings the MCS in earlier, as you can see in a few posts before, to IAD by 9pm.  Here is the dewpoints and LIs at that time.  Still pretty juicy/unstable.

 

post-1746-0-41577900-1466081629_thumb.pn

 

Despite what the NAM does with the crazy pivot, it brings the line in later and has really eroded the low-levels with a strong easterly fetch off the ocean.  DCA (or thereabouts) is 64/61 at midnight as the line is near IAD.  (showing a bit earlier here at 10pm)

 

post-1746-0-16816100-1466081692_thumb.pn

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