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FXUS61 KRNK 141900

Area Forecast Discussion
National Weather Service Blacksburg VA
300 PM EDT Mon Oct 14 2019

High pressure will continue to provide for dry and mild conditions 
across the region through Tuesday. A cold front and its associated 
precipitation will move across the area Tuesday night into 
Wednesday, and be followed Wednesday night into Thursday by very 
gusty winds. High pressure regains control on our weather pattern 
heading into and through the weekend.


As of 300 PM EDT Monday...

High pressure is providing from clear skies, mild temperatures, and 
low humidity values across the region. Through the overnight, clear 
skies will continue, and with the drier air, there will be a much 
less chance for any pockets of fog late tonight, as compared to what 
occurred this morning across eastern sections of the region. Tuesday 
also looks to be precipitation-free, but about ten degrees cooler 
than today. By the late afternoon, mid to high level cloud cover 
will start to move into the region from the south, in advance of an 
approaching cold front to our west.

Confidence in the above portion of the forecast is high.


As of 300 PM EDT Monday...

An active more amplified weather pattern is anticipated for mid-
week.  The southern stream which has been an absent player for 
months is finally showing signs of becoming a routine producer of 
short wave energy and yeilding an opportunity to tap the Gulf of 
Mexico as a moisture source.  This energy when phased with the more 
progressive northern stream, should begin to energize healthier areas 
of mid-latitude low pressure, stronger/colder frontal passages, and 
yielding wider swaths of precipitation.

The first in a series of mid-latitude waves will impact our region 
beginning Wednesday.  A shortwave digging through the northern 
stream is expected to amplify as it crosses the Ohio Valley and 
Great Lakes, the parent Low deepening to about 994 mb as it occludes 
over southern Ontario.  Models indicate southern stream energy which 
is initially strung out along the Gulf Coast will get drawn 
northward into parts of the southern Appalachians and Mid-Atlantic 
before phasing with the northern stream off the mid-Atlantic Coast 
and spawning a healthy area of low pressure to the tune of about 975 
mb over the New England maritime Thursday. 

For our forecast area there are a number of forecast challenges, the 
most critical being rainfall, which we desperately need.  In spite 
of the potential Gulf of Mexico connection from the southern stream, 
there is a stationary surface front along the Gulf Coast. As flow 
aloft overruns this front, showers/thunderstorms will become more 
prolific over the Southeast states.  This is good for the Southeast, 
but this deeper convection may rob us of what could be a more 
bonafide rain event for our area (something that would produce in 
excess of an inch). The cold front associated with the northern 
stream will likely pass through our forecast area prior to the 
deeper southern stream moisture getting into the area, and limit our 
QPF to a half inch or less. That said, we will take what we can get, 
a half inch is better than none at all.  Timing suggest the best 
opportunity for rain will be within a 12 hour window...5AM-5PM 
Wednesday. After that, all bets are off as the cold frontal passage 
associated with the northern stream cuts off any moisture connection.

Frontal passage Wednesday afternoon will feature a new set of 
forecast challenges, primarily wind and temperature. By Wednesday 
afternoon, a dry slot will advect into the southwest and central 
part of the CWA pushing the pre-frontal rain east out of the area. 
Some wrap around appears possible into the western/northwestern 
mountains, but any post frontal precipitation looks to be pretty 
limited due to the extremely dry air mass behind the front. The main 
concern for late Wednesday going into Thursday will be wind and 
sharply colder temperatures. These will be some of the strongest 
gradient winds we have seen since the spring in addition to strong 
cold air advection to go along with a strong pressure gradient. 
Northwesterly 850 mb winds of 40-45kts are progged with 85H temps of 
zero to M2 deg C. This will result in blustery northwest surface 
winds Wednesday night into Thursday (sustained 15 to 25 mph with 
gusts 30-40 mph) with temperatures bottoming out in the 30s/40s, a 
classic fall frontal passage.  Low temperatures Thursday morning 
could touch freezing in a few isolated spots, such as Burkes Garden 
and Lewisburg, but the wind should prevent frost formation.  

Thursday will be cold and blustery, really the first overly chilly 
day we have had in some time... highs confined mainly to the 40s in 
the mountains and the 50s to near 60 in the Piedmont. Wind chills 
may make it feel more like 30s and 40s much of the day.

Winds will diminish Thursday after sunset setting the stage for what 
will likely be the coldest night we have seen since last spring.
High pressure will settle over the area by early Friday morning, 
with light winds and clear skies. Thus the potential for frost as 
well as the first freeze of the season for portions of the 
mountains, especially in valleys and protected areas. Burkes Garden 
and Lewisburg are both candidates for frost/freeze and Blacksburg 
could very well be too. Further east, patches of frost will be 
possible across the Piedmont, but temperatures are expected to 
remain above freezing east of the Blue Ridge. Overnight temperatures 
will range from the low/mid 30s across the mountains, to the upper 
30s/low 40s farther east.


As of 200 PM EDT Monday...

Amplified and relatively progressive pattern is expected to continue 
across the country through the weekend and into the following week 
(Oct 20-26).  Surface High Pressure which will be centered overhead 
Friday morning, quickly sliding east by Saturday, allowing for a 
warming trend for the weekend.  Expectation is for clear skies 
Friday and Saturday, followed by increasing clouds Sunday as moist 
southerly flow increases ahead of the next storm system.  Monday and 
Tuesday are expected to be mild and wet as deep moist southerly flow 
from the Gulf of Mexico interacts with a full latitude trough, 
ingredients that are suggestive of a widespread rain event.


As of 120 PM EDT Monday...

VFR conditions are expected during the valid TAF forecast
concluding at 18Z/2PM Tuesday. Winds will mainly be on the 
light and variable side, with a few northwest gusts through this
afternoon around 10 to 15 kts.

Confidence in the above portion of the aviation forecast is

.Extended Aviation Discussion...

Tuesday night into Wednesday, weather turns active again as a 
cold front crosses the area. Expect periods of sub-VFR 
conditions with precipitation and lowering ceilings associated 
with the front's passage. Activity may be enhanced by virtue of
an area of low pressure moving northeast along the coast of
the Carolinas.

Wednesday night into Thursday, a tight pressure gradient 
develops in the wake of the passing cold front. Gusty northwest 
winds are likely during this period.

Thursday into Friday, the pressure gradient slackens and winds
trend weaker again. 

VFR conditions are expected Wednesday night into Saturday.

Confidence in the above portion of the aviation forecast is
moderate to high.





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