Area Forecast Discussion

WHAT HAS CHANGED

Upgraded entire FA where the growing season is active to Freeze Warnings.

KEY MESSAGES

- (1) Colder early this week with a fire weather threat today.

- (2) Widespread freeze expected tonight into Tuesday morning.

- (3) Warmer temperatures mid to late week, then becoming unsettled this weekend.

DISCUSSION

KEY MESSAGE 1...Colder early this week with a fire weather threat today.

A secondary cldfrnt will cross early this morning with high pressure building in its wake.

Very dry air will move overhead today. However, there is a layer between roughly 6,000 and 12,000 feet where notable moisture is present. The thought is scattered to broken stratocu and wave clouds will develop out of this, especially as the secondary front pushes through early today, then the trailing shortwave/upper-level trough pivot overhead this afternoon. A few sprinkles or a pop up shower can't be ruled out (with a little snow likely above 2500 feet over the mtns). The nose of the shortwave aloft crosses roughly between I-70 and I-64 today, and even if precip evaporates before hitting the ground (virga), very steep low-level lapse rates could result in some enhanced gustiness. Frequent gusts of 20 to 30 mph are expected again this aft, with peak gusts of 35 to 40 mph possible, mainly at higher elevations.

Dry and breezy conditions are expected through early this week. Please refer to the Fire Weather section below for more details on the fire weather threat today.

KEY MESSAGE 2...Widespread freeze expected tonight into Tuesday morning.

High pressure builds overhead tonight into Tue leading to lighter winds. The cold, dry airmass, clear skies and light to calm winds tonight into Tue morning are likely to bring widespread freeze conditions aside from the major urban centers and away from larger bodies of water. Therefore, have upgraded entire Freeze Watch to a Freeze Warning.

This is ~10 days past the median date of the last spring freeze based on 1991-2020 climatology for areas along/east of I-81. Given the warmth early this spring, many areas are ahead of schedule from a growth stand point so this freeze could be rather impactful.

There are no frost/freeze headlines for the Alleghenies as the growing season has not started there yet.

KEY MESSAGE 3...Warmer temperatures mid to late week, then becoming unsettled this weekend.

As Canadian high pressure slides off toward the S, a quick moving cldfrnt crosses the region by mid-week. There will not be a whole lot of moisture to work with, so any rainfall amounts are likely to be meager in nature. Some instability in the atmosphere could produce a few thunderstorms, particularly during the aft hours.

After a chilly start to the work week, ensembles agree on a marked warm up through the middle to latter portions of the week. High temps could push back into the low/mid 80s by Fri ahead of another system likely to bring a return of rain by the second half of Fri. A threat of showers continues through much of the weekend before the frontal system exits east of the region by late in the weekend. On Sun, the latest forecast package calls for highs returning to the 60s. This eventually all lends itself to a cooler finish to the month of April.

AVIATION /06Z MONDAY THROUGH FRIDAY/

Light winds continue through daybreak. A secondary cldfrnt will bring gusts of 20 to 30 knots today with a spotty shower possible. Otherwise, VFR conditions Tue. Winds shift to S by Tue, then SW Wed. Prevailing VFR conditions Wed, although a brief reduction to sub-VFR can't be ruled out in any SHRA.

Behind the progressive mid-week system, VFR conditions are likely for Thu into the first half of Fri. WAA showers are possible by Fri aft which could be accompanied by a few restrictions. Initial winds will be out of the NW on Thu before becoming mainly w'ly on Fri. A shift to se'ly is possible by Fri night.

MARINE

Winds remain light through daybreak increase again today with a secondary front. Light winds tonight turn s'ly Tue with additional SCAs possible late Tue into Wed.

Sub-SCA level winds are expected late Wed with winds out of the SW/W.

Expect sub-advisory level winds for both Thu and Fri. Weak gradients will favor multiple wind shifts before turning mainly S/SE by Fri night.

FIRE WEATHER

Substantial drying occurred yesterday following a relatively weak frontal passage in terms of moisture. Gusty winds and mostly sunny skies all afternoon likely sufficiently dried fuels in any areas that got less than a quarter inch of QPF. Some areas of the Shenandoah Valley and central VA piedmont fall into this category. These same areas have been the driest recently, and may also end up with the lowest humidity this afternoon. That, coupled with the breezy conditions, results in an elevated threat for the rapid spread of fires. The potential of a more substantial cumulus field, recent greenup, and at least some rain across the area may keep a more significant threat at bay. However, a Fire Danger Special Weather Statement remains in effect for today.

LWX WATCHES / WARNINGS / ADVISORIES

DC...Freeze Warning from 2 AM to 10 AM EDT Tuesday for DCZ001. MD...Small Craft Advisory from 6 AM this morning to 9 PM EDT this evening for MDZ008. Freeze Warning from 2 AM to 10 AM EDT Tuesday for MDZ003>006- 008-011-013-014-016>018-503>508. VA...Freeze Warning from 2 AM to 10 AM EDT Tuesday for VAZ025>031- 036>040-050-051-053>057-501-502-505>508-526-527. WV...Freeze Warning from 2 AM to 10 AM EDT Tuesday for WVZ051>053. MARINE...Small Craft Advisory from 6 AM this morning to 9 PM EDT this evening for ANZ530-531-535-536-538>540-542. Freeze Warning from 2 AM to 10 AM EDT Tuesday for ANZ530. Small Craft Advisory from 6 AM this morning to 4 AM EDT Tuesday for ANZ532>534-537-541-543.