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FXUS61 KRLX 041849
AFDRLX

AREA FORECAST DISCUSSION
National Weather Service Charleston WV
149 PM EST Fri Dec 4 2020

.SYNOPSIS...
Low pressure crosses south of the area today into tonight. A 
cold northwest flow may allow for light snow in the mountains 
Saturday/Saturday night. Dry but cold Sunday.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 925 AM Friday...

Adjusted the sky grids over the mountains to completely overcast
and made some minor changes to the max temperatures today. Light
rain continues to stream in from southwest to northeast this
morning, continuing through the day and shifting into the
mountains tonight.

As of 630 AM Friday...

Upped POPs for our southwestern extent of the forecast area this
morning as some observations denote that rain has started to
reach the surface. This will continue to overspread portions
east of the Ohio River Valley through the morning as surface low
pressure strengthens south of the region. 

Also freshened up temperatures and dew points this morning. With
rain already reaching the surface in the Beckley area, dew
points were coming in higher than the previously drier solution made
with the initial issuance.

As of 220 AM Friday...

A quiet night is in progress amid increasing mid to upper level
clouds ahead of our next system, which is currently undergoing
cyclogenesis in the Mississippi Valley. As surface low pressure
develops to our south, the forecast area will find itself 
within the western periphery of the disturbance, which will be 
enough to enforce a washout for the end of the work week. Early 
morning forecast soundings suggest it'll still be a few hours 
before the lowest levels of the atmosphere moisten enough for 
precipitation to reach the surface.

By daybreak, the first batch of rain will flow in from the 
Tennessee Valley and up through the central and eastern portions
of the forecast area. As the low continues to intensify in the
Carolinas and up into Virginia, jet dynamics aloft will aid in 
feeding likely POPs east of the I-77 corridor through the day 
and start of the overnight period.

The center of the low will propagate along the eastern seaboard
up into New England by the conclusion of the period. A cold 
front will follow in quick succession behind the departing low, 
sending a colder airmass down from the Great Lakes and tapering 
shower chances from west to east. Precipitation still residing 
over the higher terrain late tonight will change over to a mix 
of rain and snow showers heading into the weekend, with a measly
half an inch to an inch of snow projected along the ridgetops.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 148 PM Friday...

A complex upper level pattern is expected to develop late weekend 
and early next week and might support a light rain and/or snow event 
across the region late Sunday into Monday. On Sunday, an upper level 
low is expected to be moving eastward across the lower Mississippi 
Valley and a pair of shortwaves in the northern stream will be 
diving southward with the leading one moving from the northern 
plains towards the Ohio Valley and secondary shortwave dropping into 
the Great Lakes. The main question is whether these three features 
merge together and help support a deeper upper trough and associated 
surface low that may track across the southeast US, which would be a 
more favorable precipitation solution across the region and is what 
the latest ECMWF continues to suggest. However, the other
scenario, which the latest GFS suggests, shows less phasing 
with these three features and thus, possibly resulting in a 
surface low that develops further east and ultimately less 
precipitation chances for our area. Given these scenarios, there
still remains considerable uncertainty with the forecast in the
late Sunday into Monday timeframe but it does appear that 
regardless of the outcome, overall precipitation should be 
fairly light if the more phased solution verifies. However, if 
this system materializes, light snow would be the dominant 
p-type Sunday night with temperatures well below freezing area-
wide and since temperatures are expected to around 10 degrees 
below normal on Monday, we should remain snow in the mountains 
and possibly a rain/snow mix elsewhere. Thus, trends will need 
to be monitored in subsequent model runs before there is more 
confidence with this system. 

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
As of 148 PM Friday...

An upper level trough across the eastern US will maintain below
normal temperatures at the beginning of the long term period,
but temperatures will gradually increase each day as the trough
shifts east and an upper ridge moves in. As a result, high temperatures
should return to near normal values on Wednesday and above normal
values by Thursday. In addition, little to no precipitation chances
are expected at this time as surface high pressure is expected to
dominate the region through late week. 

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
As of 1250 PM Friday...

Light rain continuing to overspread the region as a low pressure
system passes through the Tennessee Valley. Overall, expecting
deteriorating conditions as the lower levels of the atmosphere
saturate and any light wind today going calm alter this evening
into the overnight. IFR ceilings and IFR fog settle in primarily
after 00Z Saturday give or take a couple of hours depending on
site. A reinforcing weak front aloft will keep the low ceilings
in place into Saturday after 12Z, although improvements to MVFR
can be expected as of this issuance.

FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z SATURDAY...
     
FORECAST CONFIDENCE: Medium to High.

ALTERNATE SCENARIOS: Timing of sub-MVFR ceilings may vary 
in the forecast. Brief visibility restrictions could arise 
within heavier showers.

EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY
OF WFO FORECAST TO AVAILABLE MODEL INFORMATION:
H = HIGH:   TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.
M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS.
L = LOW:    TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL.

UTC 1HRLY       18   19   20   21   22   23   00   01   02   03   04   05
EST 1HRLY       13   14   15   16   17   18   19   20   21   22   23   00
CRW CONSISTENCY  H    H    H    H    H    H    M    H    H    H    H    L
HTS CONSISTENCY  M    H    H    H    H    H    H    H    H    M    H    H
BKW CONSISTENCY  H    H    H    H    M    H    H    M    M    H    H    M
EKN CONSISTENCY  H    M    L    M    H    H    H    H    M    M    H    M
PKB CONSISTENCY  H    H    H    H    M    M    M    M    M    H    H    H
CKB CONSISTENCY  H    H    M    M    M    L    H    M    M    H    H    H

AFTER 18Z SATURDAY...
Periods of IFR conditions possible within upslope snow showers
Saturday into Saturday night.

&&

.RLX WATCHES/WARNINGS/ADVISORIES...
WV...None.
OH...None.
KY...None.
VA...None.

&&

$$
SYNOPSIS...26/RG
NEAR TERM...26/MEK
SHORT TERM...RG
LONG TERM...RG
AVIATION...26