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FXUS61 KRNK 190724

Area Forecast Discussion
National Weather Service Blacksburg VA
324 AM EDT Fri Jul 19 2019

High pressure will build across the region through the weekend 
resulting in a 3 day heat wave that will feature temperatures 
about 10 degrees above normal. A cold front should cross the 
area Monday bringing cooler and less humid weather by the middle
of next week.


As of 250 AM EDT Friday... 

Quiet weather this morning will turn to hot weather today, as 8h 
temps rise to 21 to 24C. There are no changes planned to the current 
heat advisory, but thinking a westerly downslope component to the 
low/mid level winds may drop dewpoints a couple degrees this 
afternoon east of the mountains. Still will keep the advisory, 
despite possibly not getting to 105 degrees for the heat indices for 
2 consecutive hours. This heat has been advertised for the past 
week, so should not come as a surprise. 

As far as thunderstorm chances, there may be just enough weakness 
in the upper ridge to allow for a few storms over the mountains 
today, but coverage will be less than Thursday. Have cut pops back 
to 20-30 at best.

Should see plenty of sunshine today, with highs in the mid 80s to 
near 90 in them mountains, to 90s east, ranging from the lower 90s 
in the NC foothills to upper 90s east of Lynchburg and Danville. 
Heat indices will peak out around 105 degrees from Lynchburg to 
Danville east, just over 100 across the VA foothills and Roanoke 
Valley, and mid 90s across portions of the New River Valley and 
Alleghany lower elevations such as Covington. To escape the heat you 
will nee to head to Mt Rogers or Beech Mountain. Despite the
heat, none of our climate sites are expected to get close to
record highs today.

Showers/storms are going to fade in the evening. Skies will be 
mainly clear. Some models are showing potential for an isolated 
storm overnight with a vort lobe moving across the central 
Appalachians, so could see something across the WV mountains toward 
the Mountain Empire late tonight. 

No change in the forecast with lows in the upper 60s to lower 70s 
mountains, to mid 70s east.

Forecast confidence is high for this cycle.


As of 320 AM EDT Friday...

Posted an Excessive Heat Watch for Buckingham, Appomattox, 
Charlotte and Halifax counties Saturday into Sunday.
This will likely be the warmest stretch of weather for our forecast 
area so far this summer. The heat and humidity will contribute to an 
extended stretch of elevated heat indices.  With 850 mb temperatures 
commonly into the low to mid 20s Celsius, this will lead to daytime 
ambient high temperatures into the mid/upper 80s to the mid/upper 
90s this weekend. Increasing cloud cover on Sunday may help knock 
ambient high temperatures down a couple degrees compared to 
Saturday. Little relief is expected at night, with lows in the upper 
60s to the mid to upper 70s Saturday nights, and lows in the mid-
upper 60s to low-mid 70s Sunday night. 

For headlines, excessive heat criteria for our forecast area 
involves maximum heat indices of 110F or greater with intervening 
lows of 77 or greater. The forecast brings Buckingham County 
southward to Halifax county to levels close to that criteria, while 
falling short elsewhere. Will post addition heat advisories for this 
period once we enter the shorter range. Each afternoon, there should 
be some mixing that in the afternoon helps locally reduce dewpoints 
as temperatures rise that could affect (e.g. reduce) heat index 
values. Will continue to message the heat in the HWO. 

Under the large subtropical ridge, convective chances through the 
period are generally on the smaller side into Sunday. If any storms 
were to develop, these would tend to be confined to the terrain. 
Into Sunday, the subtropical heat ridge fractures, leaving us in a 
weakness in the ridge. This should foster generally greater cloud 
cover and greater thunderstorm coverage. Possible that one or two 
may become strong and produce gusty winds and brief heavy rainfall, 
but it remains low-predictability which area(s) may see this threat 
relative to others.

Take extra precautions...if you work or spend time outside.  When 
possible...reschedule strenuous activities to early morning or 
evening. Know the signs and symptoms of heat exhaustion and heat 
stroke. Wear lightweight and loose fitting clothing when possible 
and drink plenty of water.


As of 115 PM EDT Thursday...

On Monday, we expect to see a full transition from the hot upper 
ridge that has been over the region, to one of a longer wave trough 
positioned over the East Coast through at least mid-week. At the 
heart of this transition will be a strong cold front which is 
expected to cross the region on Monday. Showers and storms are 
forecast to be in progress by the mid to late morning across western 
sections of the area with all areas of the forecast area having 
greater than a 50 percent chance of showers and storms during the 
afternoon. Temperatures on Monday will be notably cooler as compared 
to the several days before thanks to the passage of the cold front, 
abundant cloud cover, and precipitation across the area. Highs will 
range from the upper 70s to around 80 across the mountains with mid 
80s to near 90 across the Piedmont. 

As we progress into mid-week, the upper trough builds even more 
across the east with surface high pressure building into the mid-
Atlantic. Precipitation chances will linger Monday night into 
Tuesday across mainly eastern and southern sections of the region, 
nearest the cold front which is expected to stall near the NC/SC 
border. The general trend across the entire area will be for drier 
and cooler weather. By Wednesday temperatures are expected to 
average around five degrees below normal for this time of year.


As of 118 AM EDT Friday...

Expect a period of MVFR at LYH/DAN this morning with IFR or
lower at BLF/LWB and BCB with mainly fog and/or low cigs.

Friday should generally bring VFR conditions to the forecast
area once the morning fog/low clouds burn off. A broken layer of
CU will scatter out by late morning. 

Isolated to scattered thunderstorms will be possible across 
mainly the southwest and far west part of the CWA, which at this
point should not impact any of the TAF sites.

Forecast confidence is high, except medium on how low
clouds/vsbys drop at times this morning in the west.

.Extended Aviation Discussion...

For late Friday night into Saturday, high pressure will 
strengthen overhead, with subsidence curtailing, but not 
completely eliminating, the potential for diurnally driven 
showers and storms Saturday afternoon. However coverage looks 
even less than Friday with any storms likely confined to the 
higher peaks along the Blue Ridge at this point. Otherwise, VFR 
outside of some late night fog in the mountain valleys, with 
potential to restrict visibility for a few hours prior to 
daybreak at terminals such as KLWB and KBCB. 

A bit better coverage of showers/storms is expected late Sunday
and Monday, associated with the approach and passage of a cold 
front. The front will also bring a wind shift later Monday. This
front may slow down enough to keep storm chances east of a ROA-
TNB line Tuesday.


VA...Heat Advisory from noon today to 8 PM EDT this evening for 
     Excessive Heat Watch from Saturday afternoon through Sunday 
     evening for VAZ046-047-058-059.
NC...Heat Advisory from noon today to 8 PM EDT this evening for 



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