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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
359 am EDT Monday Apr 27 2015


An upper level trough to the north will move through the area today.
High pressure will move into the area Tuesday. Low pressure is
expected to track across the southeastern U.S. During the second
half of the week.


Near term /today/...

Clear skies at this time...but that will change as clouds across PA track southward into
the County Warning Area. This is in asso west/ an upper level short WV embedded in what
is a somewhat unusual synoptic pttn for late Apr west/ a closed low
spinning in the Gulf of ME. Rain shower will be possible..primarily across the
nwn 1/3 of the forecast area late this morning through middle afternoon.

As has frqntly been the case lately temperatures expeceted to be below normal. West/
the central shen vlly being the last to cloud over temperatures should rise
to the m60s...but much of the rmdr of the forecast area will top out in
the u50s/l60s.


Short term /tonight through Tuesday/...

The synoptic pttn is going to be slow to change through Tue: the
aforementioned upper low looks to spin slowly out to sea. High pressure
will work its way into the middle Atlantic during Tuesday. Lows tonight will be in the
l40s. West/ more insolation Tuesday temperatures should climb back into the
u60s - still a few degrees below normal.


Long term /Tuesday night through Sunday/...

An active and complex storm system approaching from the Gulf Coast
region is certain for the second half of the work week. Model
divergence for the system as it nears the area toward middle week adds
uncertainty. The 00z version of the ecm keeps a more southern-stream
system and keeps it as more of an open wave upon arriving over the
Atlantic coast Wednesday into Thursday. Instead of an intensification of the system
from a back side upper vorticity diving down from the Great Lakes pushes the system off the coast. The GFS however has
quite the aggressive depiction in its 00z run...taking a deepening
upper cut off low over the Ohio Valley and sliding it into the back
side of the precipitation shield over the Carolinas at about the same time.

The addition of this potent upper vorticity diving down out of southern
Canada adds the energy the system would need to do an intense
phasing...similar to system in the middle of winter over the middle-
Atlantic. This aggressive solution brings an intense surface low hugging the
Delaware-Maryland-Virginia coast late Thursday into Friday. Gusty winds over the Bay and a
cold rain over the rest of the mid-Atlc. Raised probability of precipitation into the medium
chance categories from late Wednesday into early Friday...but still not
confident in GFS solution west/ the intensity/duration and all the proper
factors coming together for such an intense storm system. Blended
some of the bias-corrected values and leaned on the Euro in a
long- term blend of various weather elements for this time period. Will
monitor trends.

The more aggressive and recent GFS run keeps the system over the
area for much of the day Friday while the Euro has a bulk of the
feature well off the coast by then. Either way...a multi-day period
of high pressure will return from the weekend and likely into early
next week.


Aviation /07z Monday through Friday/...

VFR conds expeceted today through Tuesday. A few rain shower are expeceted late this
morning/afternoon but covering will be low so not specifically mentioned in the
tafs. Winds will gust to a20 kts from the northwest late this mrng/aftn.

Low confidence in the possible effects of a low pressure system that
will approach the area during the middle of the week. Possibly a
couple of days of rain and gusty winds...but a less intense solution
would be for the system to pass just south of the area and slide off
the Atlantic coast.



Small Craft Advisory has been extend for the majority of the waters through Tuesday. Low
pressure in the Gulf of ME today will track slowly east...but west/ high pressure
moving into the region Tuesday the pressure gradient will remain in place and g20 expeceted
through middle afternoon Tuesday.

A potent low pressure system over the deep south early this week
will have the potential to bring small craft and possibly gale
conditions to the waters from late Wednesday into Friday.


Lwx watches/warnings/advisories...
District of Columbia...none.
Marine...Small Craft Advisory from 8 am this morning to 4 PM EDT
Tuesday for anz530>534-537>543.
Small Craft Advisory from 8 am this morning to 8 PM EDT this
evening for anz535-536.



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