Area Forecast Discussion
Issued by NWS Huntsville, AL

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FXUS64 KHUN 250210

Area Forecast Discussion
National Weather Service Huntsville AL
910 PM CDT Thu May 24 2018

.NEAR TERM...(Tonight)
Issued at 910 PM CDT Thu May 24 2018

The area stayed for the most part shower/storm free today as the
result of a surface high to our north and a rather dry profile, which
is evident in the 00z OHX sounding. To our NE there are a few storms
still going but those are stuck to the terrain and with weak flow
aloft don`t believe these will move towards the area. Latest RAP
analysis shows a region of higher MUCAPE and Theta-E over areas E/SE
of Huntsville. A weakening line of storms moving just north of ATL
does appear to be moving towards the better Theta-E and they could
hold together long enough to clip portions of DeKalb and Marshall
counties this evening. Made some adjustments to PoPs to account for
those storms.

In terms of temps, nudged values down in the typical cool spots but
didn`t make any other changes to the overall forecast for tonight.
Lows in the mid to upper 60s.

.SHORT TERM...(Friday through Saturday Night)
Issued at 224 PM CDT Thu May 24 2018

The MCV in GA is forecast to lift back northeast on Friday as
shortwave troughs in the central Plains move into the lower MO valley
and Ozark plateau. This will enable weak southerly flow to develop in
low levels and lift the convergence zone (albeit weakening)
northeastward through the TN valley on Friday afternoon and evening.
This along will be enough to bring greater chances of thunderstorms
during peak heating. The elevated terrain along the Cumberland
Plateau may also aid development as well. Exact timing and locations
of precipitation will largely be impacted by mesoscale features which
the NAM and GFS are showing with convectively enhanced vorticity
centers moving through both Friday night into Saturday. The NAM in
particular shows a wave forming over southeast MS that lifts north
and merges somewhat with the incoming 5h trough axis which should lie
from central KY through northern MS. This may keep more widespread
activity to our NW on Friday night into Saturday. Nevertheless, will
keep PoPs in the chance range from Friday night through Saturday
night (highest during peak heating Saturday).

.LONG TERM...(Sunday through Wednesday)
Issued at 224 PM CDT Thu May 24 2018

Much like yesterday, the extended portion of the forecast looks to
be a soggy one, as we welcome the unofficial start of Summer with
Memorial Day. Daily chances for showers and storms will be the rule,
with the exception being slightly less coverage during the late
evening/overnight hours. The higher-than-normal rain/storm chances
are thanks to a developing upper low, currently over the Yucatan
Peninsula, that will meander N over the open GOMEX. Whereas yesterday
the GFS was the outlier with the furthest `track` to the E, making
landfall in the Ern Panhandle of FL, today it joins the rest of the
model consensus with a more Wwrd track. Model consensus this
afternoon has a general `landfall` near Biloxi ~12Z Monday, with a
few members skirting SErn LA. Either way, with a more Wwrd track,
confidence is increasing in higher rainfall amounts compared to a
more Erly track (keeping much of the heavy rainfall locked further
S/E of the local CWFA). That said, the highest rainfall totals with
wherever this sub/tropical feature ends up will definitely be greater
along the coast, lessening as you move inland. This feature looks to
meander/wobble across the region for much of the week as it
gradually weakens, though higher-than-normal moisture will remain,
making for a muggy week ahead.

While confidence is high that tropical moisture streaming into the
area will provide near-daily-max PWat values through the week
(1.8-2.1"), torrential rainfall will be the primary hazard of
concern. This may lead to hydrologic concerns (flash and river
flooding) toward the end of the week if several heavy rounds of
rainfall traverse the region. In addition to the rainfall/flooding
threat, gusty winds ~40mph will be the secondary hazard (thanks to a
couple hundred Joules of DCAPE present each aftn), especially within
any stronger storms that can develop during the week ahead.

Again, the forecast for the extended heavily depends on exactly where
this feature tracks, so stay tuned for further forecast updates.

Temperatures during this timeframe will be generally in the
lower/middle 80s for daytime highs, with morning lows only falling
into the upper 60s to around 70 degrees. Only late in the period will
temperatures approach 90 degrees, and it`s when the remnants of this
sub/tropical feature finally get picked up in H5 flow by Thu/Fri that
this occurs. This will clear things out perhaps in time for the
weekend as an H5 ridge building across the Central Plains finally
shift E over our area, though models diverge regarding a disturbance
in NW flow by Sat. This would bring yet more rainfall to the region,
but details are too murky to buy this solution just yet.


.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 636 PM CDT Thu May 24 2018

VFR conditions prevailed again today and should continue through much
of the period. Winds become more southerly after 14Z Friday and this
will trigger an increase in low level moisture. Added a Prob30 group
for Friday afternoon as coverage of storms should be higher but still
unable to narrow a time down for moving over the terminals.




NEAR TERM...Stumpf

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