496
FXUS61 KRNK 132205
AFDRNK

Area Forecast Discussion
National Weather Service Blacksburg VA
605 PM EDT Mon May 13 2024

.SYNOPSIS...
A low pressure system will cross the Mid Atlantic during
Tuesday and Wednesday to bring showers and thunderstorms. Weak
high pressure should provide drier air for Thursday, but
another low pressure system will bring more rain for the end of
this week.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 600 PM EDT Monday...

A feeder-like band of showers are coming across SC/NC this
evening. Observations are reporting rain with dew points in the
mid to upper 50s. As showers advance over an area, dew points
jump into the low to mid 60s.

For the immediate forecast area, dew points are in the mid to
upper 40s, but will jump into the 50s as moisture continues to
advance northward this evening. Bumped up timing a few hours for
rain entering the NW NC mountains this evening. Rainfall
amounts will be a few hundredth of an inch. Once the initial
band of showers tracks north of Highway 460 later this evening,
there should be a lull in measurable rainfall south. A wave will
then move over the area Tuesday morning with more areal
coverage of rain for the entire area.


Previous forecast as of 125 PM EDT Monday...

Key Messages:

1) Confidence is high for rain arriving later tonight and
persisting through Tuesday.

2) Thunderstorms will be possible by Tuesday afternoon.

Some dense cirrus has been spreading across locations south of
Route 460 today as a low pressure system approaches the central
Mississippi River Valley. The 12Z RNK sounding was still dry
with only a precipitable water value of 0.38 inches, so any rain
chances are delayed until later tonight. A southerly breeze at
the surface combined with an upper level ridge building overhead
should boost temperatures into the 60s and 70s this afternoon.

The low pressure system will push a warm front towards the
southern Appalachian Mountains tonight, which will provide
increasing chances of rain. Instability is zero overnight as
depicted in the high-resolution models, so no thunderstorms are
expected until later on Tuesday. The highest chances of rain
were placed along and east of the Blue Ridge in reasonable
agreement with the models. With cloud cover and warm advection
taking place tonight, low temperatures will only fall into the
50s for most locations, which is about fifteen degrees higher
than the temperatures observed earlier this morning.

Tuesday morning will start cloudy with rain spreading across
the Mid Atlantic. Lift from the warm front may spark enough
instability aloft by Tuesday afternoon to introduce chances of
thunderstorms. While there could be some heavier downpours in
these storms, antecedent conditions are still rather dry from
the past week, so the flooding threat is low. The highest odds
of storms are located either in the mountains west of the Blue
Ridge or across northwest North Carolina and southside Virginia.
Temperatures will only reach the 60s for highs due to the
abundant cloud cover from a moist southeast flow.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 215 PM EDT Monday...

Key Messages:

1. Clouds and Showers Wednesday
2. Partial clearing Thursday

Shower and storm chances continue into Wednesday, as moisture
wraps around the low as it tracks through the Mid Atlantic. By
early Thursday morning, 500mb ridging builds back into the area,
in response to another trough deepening over the Rockies and
western US. A drier airmass fills into the area behind the
front, reducing shower and storm coverage for Thursday.

Temperatures will generally be near normal for this forecast
period, cloud cover keeping overnight lows on the mild side,
in the 50s and 60s. High temperatures will gradually warm
through the period, with Thursday trending 5 degrees warmer
compared to Wednesday.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 245 PM EDT Monday...

Key Messages:

1. Showers and storms possible again Friday, lingering into the
weekend.
2. Temperatures near normal Friday and Saturday, warming above
normal by Monday.

Weather pattern has shifted to a 3-day shortwave cycle with
weather systems, waves of low pressure, passing about every 3-4
days. Long range shows next wave to pass early this weekend,
followed by another system the middle of the following week. All
features this late in the spring now conducive of
thunderstorms, so forecast will reflect more of a showery/stormy
sort of regime, but keep in mind that it will not rain the
entire time. Key word is shower... something that lasts for 45
minutes or less when it occurs. Same is true for our severe
weather chances. Probability remains low unless something can
materialize during peak heating. Attm, model differences in
timing make it difficult to pin down anything mesoscale within
this time frame, so nothing of great concern. Of a bit more
confidence is potential for localized heavy rain which can just
as easily occur at night as opposed to the day, especially if
there is a focusing mechanism. PWATs are forecast to remain
high the next 7-10 days...exceeding the 90th percentile on many
of these days, so rain efficiency will be high wherever it
rains.

Focusing on the weekend, mid level ridging will slide east of
the area Friday with flow aloft turning more southwesterly.
Temperatures will continue to warm as low pressure approaches
the area from the west, bringing the next opportunity for
wetting rainfall, mainly in the form of showers and
thunderstorms. As noted, there are timing differences in the
deterministic models so will broadbrush the pops both Friday
and Saturday...then tail them off the first of next week as the
weather system clears the area.

After the weekend system, temperatures trend warmer yet, with
highs by Monday above normal. This may set the stage for an
even more robust system the middle of the following week.
Higher temperatures, yield greater CAPE and stronger updrafts.

&&

.AVIATION /22Z MONDAY THROUGH SATURDAY/...
As of 125 PM EDT Monday...

VFR conditions are expected at all terminals through the
remainder of today with a south breeze. However, a low pressure
system will approach from the southwest tonight, which is
responsible for the cirrus spreading across the Mid Atlantic
today. Ceilings should lower to MVFR after midnight tonight and
fall further to IFR by early Tuesday morning as rain becomes
more widespread. Patchy fog and a chance of LIFR ceilings may
also accompany the rain in the morning.

Ceilings will not rise much during Tuesday due to a moist
southeast flow. Heavier rainfall rates are possible for LYH and
DAN as the warm front from this low pressure system lifts
northeastward. Chances of thunderstorms will gradually increase
by Tuesday afternoon due to increasing instability aloft, but
most terminals are expected to remain cloudy with poor flying
conditions throughout the day.

Extended Aviation Outlook...

Poor flying conditions will continue through Tuesday night into
Wednesday as a cold front approaches from the west. Scattered
showers and thunderstorms should continue through Wednesday
evening but start to fade by Wednesday night as the cold front
exits. VFR conditions should return for most terminals by
Thursday due to weak high pressure passing to the north.
However, another low pressure system could arrive during Friday
afternoon into Saturday to bring low ceilings and scattered
showers and thunderstorms.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.

&&

$$

SYNOPSIS...PW
NEAR TERM...PW/RCS
SHORT TERM...AS/PM
LONG TERM...PM
AVIATION...PW